Temporal minor slow and sharp EEG activity and cerebrovascular disorder.

The clinical significance of temporal minor slow and sharp activity (TMSSA) is discussed on the basis of earlier literature and personal observations (209 patients, 227 EEG records). This pattern consists of mixed 2-7/sec and 8-14/sec activity with intermingled minor sharp transients (occasionally even frank spikes) over the anterior temporal-midtemporal region and, in the vast majority (84% in our material) predominantly on the left side. This pattern is most prominent in early drowsiness, and may change to rhythmical spiky discharges in light NREM sleep ("wicket spikes"). The origin of TMSSA is unclear. There is reason to believe that hippocampic ischemia might be the underlying substratum but the evidence remains tenuous. Vertebrobasilar artery insufficiency states may result in TMSSA since the hippocampus largely depends on this vascular system (via posterior cerebral artery). The occurrence of TMSSA usually represents a mild abnormality of potentially considerable clinical significance.